A fuel cell stack is a device generating, as a main power source of a fuel cell vehicle, electricity through a redox reaction of hydrogen and oxygen.
In general, the fuel cell stack is formed by stacking a plurality of unit cells including a membrane-electrode-assembly (MEA) and separator plates disposed on both sides of the MEA.
The MEA includes a polymer electrolyte membrane, an anode electrode provided on one surface of the polymer electrolyte membrane, and a cathode electrode provided on an opposite surface of the polymer electrolyte membrane. The separator plate includes a hydrogen channel for supplying hydrogen to the anode electrode, an air channel for supplying air to the cathode electrode, and a coolant channel for supplying coolant.
The anode electrode receives high-purity hydrogen supplied from a hydrogen storage tank through the hydrogen channel of the separator plate. The cathode electrode receives air in the atmosphere, which is supplied by an air supply device, such as an air compressor, through the air channel of the separator plate. Then, protons and electrons are generated in the anode electrode as the oxidation reaction of hydrogen proceeds. The generated protons and electrons are moved to the cathode electrode through the polymer electrolyte membrane and the separator plate. Additionally, in the cathode electrode, the reduction reaction proceeds in which the protons and electrons moved from the anode electrode and the oxygen in the atmosphere, which is supplied from the air supply device participate, thereby producing water and electrical energy resulting from the flow of the electrons.
Meanwhile, recently, there has been developed and used a unit cell provided to transfer air through a formed porous body or a foamable porous body by interposing the formed porous body and the foamable porous body between a separator plate and a gas diffusion layer instead of forming the air channel in the separator plate. When an air passage is formed to transfer air by using the formed porous body or the foamable porous body, the porosity of the formed porous body or the foamable porous body has to be adjusted for the design purpose of the unit cell. However, since the foamable porous body has a geometric shape randomly formed, it may be difficult to precisely adjust the porosity for the design purpose. In addition, to fabricate the formed porous body, a mold is required due to the characteristic of the fabrication process. Accordingly, the formed porous body has problems of requiring many costs in installing the mold and requiring an additional cost to change the structure of the mold in the case that a shape change is required while optimizing the formed porous body for the design purpose.